In recent years, there has been an increasing tendency for surgeons to use stapling instruments to suture body organs and tissues such as lung, esophagus, stomach, duodenum and other body organs in the intestinal tract. The use of an appropriate stapling instrument in most instances performs a better job in less time and simplifies previously difficult surgical procedures such as gastrointestinal anastomoses.
In the prior art, the early linear two and four row cutting staplers were permanent instruments into which the staples were individually hand loaded. These staplers were very expensive, bulky, heavy and difficult to load and to clean for each surgical use. An example is disclosed in U.S. Pat. No. 3,315,105. An improvement of the permanent type surgical stapler was made by providing the basic stapling instrument with a presterilized disposable staple loading unit and with an optional knife for dividing the tissue simultaneously while forming the rows of staples. An example is disclosed in U.S. Pat. No. 3,499,591. However, this improvement mainly accomplished the saving of the time previously required to load the staples by hand. It was still necessary for the basic instrument to be disassembled, cleaned, reassembled and fitted with a new cartridge and anvil for each surgical procedure, in addition to the maintenance required of the stapling instrument itself. Another problem with this type of instrument is the tendency for the jaws to spread apart at the distal end after repeated use resulting in a substantial variation in the formed staple heights between the proximal and distal ends of the staple rows.
As hospital costs have continued to increase, it has become necessary to eliminate unnecessary work and develop more efficient techniques without compromise to the surgical procedure. Consequently, disposable stapling instruments of the type disclosed in U.S. Pat. No. 4,429,695 have been developed. In the disposable stapling instrument of this patent, an actuator and knife blade assembly provides local support to the stapler jaws in the region of the knife blade and pusher bar cams. However, this stapling instrument does not provide clamping forces simultaneously along the entire length of the anvil and staple cartridge carrying portions of the stapler jaws to resist the tendency of the jaws to separate when the staples are formed. Thus, there is the possibility that rows of non-uniform staple heights will be produced. If the tissue is stapled too tightly, the blood supply is compromised and the tissue may necrose. If stapled too loosely, the tissue may hemorrhage or, in the case of hollow organs such as intestine, may also leak. Thus, both too tightly and too loosely formed staples can cause serious problems and complications.
Typically, a linear anastomotic stapling instrument includes a pair of cooperating elongate jaw members, each adapted to be inserted into internal, tubular body organs to be anastomosed. One of the jaw members supports a staple cartridge with at least two laterally spaced rows of staples, and the other jaw member supports an anvil with staple-forming pockets aligned with the rows of staples in the cartridge. Generally, a single pusher bar and knife assembly is slidable longitudinally along the jaw members to sequentially eject staples from the cartridge via camming surfaces which activate a plurality of staple drivers carried by the cartridge and associated with the individual staples to close the staples against the anvil and form laterally spaced rows of staples in the tissue gripped between the jaw members. A knife blade which trails the pusher bars cuts the tissue along a line between the staple rows. Examples of such anastomotic stapling instruments are disclosed in U.S. Pat. Nos. 3,499,591 and 4,429,695. In neither instance is any provision made for application of clamping forces simultaneously along the entire portions of the jaw members which support the anvil and staple cartridge to resist the forces exerted when the staples are formed.
In the use of stapling instruments of the above type, relatively large forces are exerted in clamping the tissue to be fastened between the jaw members, ejecting the staples from the staple cartridge, driving the staples into the gripped tissue, and forming the staples against the anvil. Such forces tend to separate the jaw members vertically and to distort the jaw members laterally, with the result that the consistency of the formed staple height is diminished, or that the staples may sometimes miss the anvil completely. This problem is accentuated in the case of a disposable stapling instrument in which relatively lightweight disposable materials are used for the manufacture of the jaw members and other components. Thus, there is a need for a disposable stapling instrument which is capable of accurate alignment of the jaw members while the staple forming operation is performed, and which provides adequate support for its elongate jaw members to withstand the large forces encountered in the operation of the stapling instrument. In addition, there is a need for a stapling instrument which produces staple rows of uniform height in the tissue gripped between its jaw members.